1. Field of the Invention
The present invention relates to water-dispersible particles for delivery of biomolecules. More particularly, the present invention relates to water-dispersible methylene urea particles for delivery of biomolecules.
2. Description of the Related Art
A continuing problem in care of large areas of cultivated vegetation is the difficulty of delivery of an agent such as a plant nutrient, fertilizer or a pesticide to the target. A practical and labor-saving approach to agent delivery in areas such as golf courses, parks, lawns, gardens and woodlands has been broadcast application of granular products containing an agent, for example via rotary spreader. Using granular products having particle sizes in the range of about 1 millimeter to about 10 millimeters, an operator can cover a large area with minimal distance traversed by the spreader itself, while applying the granular products relatively uniformly to the desired area. Unfortunately, such granular products often remain in solid or semisolid form several days following their application. This is a problem when the granular product is carrying an active ingredient such as pesticides, plant growth regulators, micronutrients, or plant growth hormones because these substances remain physically bound up with the granule so that their efficacy is reduced or delayed. This can result in loss of the active ingredient via volatilization and photodegradation with the consequence of lower efficacy and higher cost.
A further consequence of the fact that granular products often remain in solid or semisolid form for long periods following application is that the granules are subject to removal by cultural practices such as mowing with clipping removal, leaf and or yard waste vacuuming; or run-off from weather events, especially on sloping ground where the underlying soils have low percolation rates; where the ground cover is closely mown or relatively thin and sparse; and where the equipment or pedestrians traffic is high. This causes a loss of the uniformity of the biological response sought by the use of the product. In addition, product efficacy may be altered due to excessive concentration of the product within the areas treated.
The long persistence of the granular products also results in a greater likelihood that people and or animals may come into physical contact with the granules, which may result in skin irritation, sensitization, dermal absorption and toxicity. Additionally, when clothing, footwear and equipment come into physical contact with the granules, they can cause damage, corrosion or staining.
The present invention solves the problems associated with persistence of granular products by providing compositions and methods for making controlled release nitrogen pellets which are water-dispersible. The inventive pellets, when handled without coming into contact with water, have physical characteristics similar to existing controlled release nitrogen granules, allowing broadcast application. Following application, the inventive pellets disperse on contact with moisture from the treated area itself, from irrigation or from natural precipitation. The dispersion of the pellets allows the controlled release nitrogen and other active ingredients to be deposited downwards and laterally from the original position of the pellet, so that the controlled release nitrogen and other active ingredients are less likely to be removed from the treated area, ingested by small children or animals, or otherwise contacted by people, animals, clothing, footwear or equipment. Water-dispersibility also prevents wastage of any relatively expensive components of the inventive pellets since more of the ingredients reach their respective targets.
Thus, there is a continuing need for a uniformly sized, durable product in particle form which can deliver nitrogen in a controlled release manner and whose components are quickly dispersible in order to provide even delivery of active agents to target plants and organisms over a large area.